1. Field of the Invention
An embodiment of the present invention relates to the fabrication of a microelectronic substrate. In particular, embodiments of the present invention relate to a buried silicon dioxide/silicon nitride bi-layer insulator and methods of fabricating the buried silicon oxide/silicon nitride bi-layer insulator for the fabrication of microelectronic transistors.
2. State of the Art
Buried insulator substrates, such as silicon-on-insulator (SOI) substrates, have become desirable for many microelectronic technologies, including extreme scaling of metal-oxide semiconductor (MOS) and complementary metal-oxide semiconductor (CMOS) devices, advanced MOS junction-type field-effect transistors (MOSFETs), and quantum wires and dots. This is primarily because SOI fabrication processes result in increased packing densities, improved performances, better device isolations, and reduced extrinsic parasitic elements, particularly those of the source and drain, thus significantly speeding up circuit operations.
A typical process for forming a buried insulator may entail implanting oxygen atoms (for example, at a dose between about 2×1017 to 5×1017 ions/cm2 and an implantation energy between about 150 to 250 keV) into a silicon substrate to form a high oxygen concentration layer within the silicon substrate. The implanted silicon substrate is then annealed (heated) to the silicon substrate (for example, at a temperature of greater than about 1200 degrees Celsius), which results in the formation of a buried silicon oxide layer.
Although this technique results in a functional buried silicon oxide insulator, the implantation step of the process can result in a substantial amount of micro-defects in the silicon substrate. These micro-defects may lack oxygen atoms (i.e., silicon oxide insulator material) and may provide a path for electric current leakage. This electric current leakage can significantly degrade the performance of a microelectronic device. Thus, there is a need for an improved buried insulator and processes for forming the same.